Combinations containing films are commonly used for packages product such as foodstuffs, medical and pharmaceutical products, electronic products and others. These combinations generally comprise at least one layer of non-transparent material such as aluminum foil, metalized polymer film, paper or the like. These combinations often also comprise films of polyethylene, polypropylene, polyester or the like, layered on one or both sides of the non-transparent material.
One popular packaging combination consists of a layer of paper having adhesive-laminated thereto a clear heat-sealable plastic layer. The paper portion of the laminate is die-cut prior to lamination, to provide windows to view the contents of packages formed therewith. When forming a bag with this material, it is usually necessary to apply a hot melt or other adhesive on the paper/plastic back seam, and on the paper/plastic interface at the bottom of the bag.
Due to the manufacturing complexity associated with the application of adhesive on the bag back seam and bottom, it is conventional to sell pre-made bags to processors, for subsequent filling and closure. The use of pre-made bags is relatively expensive. Also, the use of adhesive lamination can result in gaps between the layers of the finished material, which gaps render the material prone to delamination, loss of barrier and insect infestation. Voids are also prone to occur where the window meets the paper. Yet further, these bags are typically not hermetically sealed.
Another popular material comprises a layer of non-transparent, heat-sealable material. Materials of this type can be used in form-fill-seal machines, of the type for producing stand-up pouches and other packages, which is advantageous to processors in terms of cost. Also advantageous, these packages are generally hermetically sealed. However, these packages suffer in terms of consumer acceptance, as consumers cannot view the contents thereof.